When I played on PS3, I found that you can actually put the marks on a slot in the hotbar. This will bring up the full menu and you can pick through any of them on your selected target. Then you move to your next target.

An easy route would be macroing in the "1" target mark in with shield lob, if you use that for pulling. I never use it unless I am pulling so it works out pretty well.

I linked my marking to Shield Lob. I find this keeps me as the 'director' of the fight, as it were and allows me to select the next target for the DPS by how much enmity a mob has accrued or by switching target priority to adds which may be more of a threat to the group.

My personal opinion in regards to number marking is that is prevents fluid tactical adjustments to combat and encourages the DPS to race ahead of the tank, making Enmity management needlessly more difficult. Additionally, as I stated above, its rigid, so in the event that a more dangerous add decides to crash the party, the mentality is to follow the numbers regardless and often leads to confusion.

And while I acknowledge there are certainly actions that can be taken to address adds, they aren't always available for a variety of reasons. True, Tanks aren't always party leaders, but they are inevitably the tactical coordinators, and as such, must (in my opinion) have a the ability to adjust to combat scenarios changing mid-fight.

Here is the macro I use for those who may be curious:

/enemysign "Circle 1" <t> /wait .5 /ac "Shield Lob" <t>

Simple and effective. Sidenote: Not sure if the /wait .5 actually works (somone told me that partial increments don't work), but I've encountered no problems to date.